/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2002-2012 OpenVPN Technologies, Inc. <sales@openvpn.net>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program (see the file COPYING included with this
 *  distribution); if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#elif defined(_MSC_VER)
#include "config-msvc.h"
#endif

#include "syshead.h"

#if defined(USE_COMP)

#include "comp.h"
#include "error.h"
#include "otime.h"

#include "memdbg.h"

static void
stub_compress_init (struct compress_context *compctx)
{
}

static void
stub_compress_uninit (struct compress_context *compctx)
{
}

static void
stub_compress (struct buffer *buf, struct buffer work,
	       struct compress_context *compctx,
	       const struct frame* frame)
{
  if (buf->len <= 0)
    return;
  if (compctx->flags & COMP_F_SWAP)
    {
      uint8_t *head = BPTR (buf);
      uint8_t *tail  = BEND (buf);
      ASSERT (buf_safe (buf, 1));
      ++buf->len;

      /* move head byte of payload to tail */
      *tail = *head;
      *head = NO_COMPRESS_BYTE_SWAP;
    }
  else
    {
      uint8_t *header = buf_prepend (buf, 1);
      *header = NO_COMPRESS_BYTE;
    }
}

static void
stub_decompress (struct buffer *buf, struct buffer work,
		 struct compress_context *compctx,
		 const struct frame* frame)
{
  uint8_t c;
  if (buf->len <= 0)
    return;
  if (compctx->flags & COMP_F_SWAP)
    {
      uint8_t *head = BPTR (buf);
      c = *head;
      --buf->len;
      *head = *BEND (buf);
      if (c != NO_COMPRESS_BYTE_SWAP)
	{
	  dmsg (D_COMP_ERRORS, "Bad compression stub (swap) decompression header byte: %d", c);
	  buf->len = 0;
	}
    }
  else
    {
      c = *BPTR (buf);
      ASSERT (buf_advance (buf, 1));
      if (c != NO_COMPRESS_BYTE)
	{
	  dmsg (D_COMP_ERRORS, "Bad compression stub decompression header byte: %d", c);
	  buf->len = 0;
	}
    }
}

const struct compress_alg comp_stub_alg = {
  "stub",
  stub_compress_init,
  stub_compress_uninit,
  stub_compress,
  stub_decompress
};

#else
static void dummy(void) {}
#endif /* USE_STUB */
